JP2023048561A - Zinc complex of hydrazide compound, and rubber reversion inhibitor - Google Patents

Abstract

To provide a zinc complex of hydrazide compound added to a rubber composition, and a rubber reversion inhibitor containing the zinc complex of hydrazide compound.SOLUTION: The present invention provides a zinc complex of hydrazide compound, and a rubber reversion inhibitor containing the zinc complex of hydrazide compound.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a zinc complex of a hydrazide compound and a reversion inhibitor for rubber.

Large tires (especially ultra-large tires for mining) are generally made of natural rubber, which is excellent in strength.

Vulcanization molding of a large tire requires a long vulcanization time due to the size of the tire. For this reason, in the vulcanization molding of large tires, a phenomenon called "reversion" may occur, which does not pose a problem in the case of small tires for passenger cars, which are mainly made of synthetic rubber. Due to this reversion, the main chain of the polymer or the sulfur cross-links formed by vulcanization are broken during long-term vulcanization, which may result in a reduction in strength and durability of the tire.

In the production of large tires, it is required to suppress reversion during vulcanization molding, and there is a demand for production of a rubber composition that is less prone to reversion.

Patent Document 1 discloses a rubber component comprising 100 parts by weight of at least one selected from natural rubber and synthetic rubber, and 0.05 to 5 parts by weight of 1,6-hexamethylene-sodium dithiosulfate dihydrate (HTS). , 0.05 to 5 parts by weight of a hydrazone compound, wherein the hydrazone compound is 3-hydroxy, N'-(1,3-dimethylbutylidene)-2-naphthoic acid hydrazide (BMH), and N'-( 1,3-dimethylbutylidene)salicylic acid hydrazide (BMS). However, the technique of Patent Document 1 does not have sufficient reversion resistance.

The rubber compositions of the prior art require further improvement in reversion resistance in order to meet the demand for improved durability of automobiles.

Patent No. 4608076

An object of the present invention is to provide a zinc complex of a hydrazide compound to be added to a rubber composition, and a rubber reversion inhibitor containing the zinc complex of a hydrazide compound.

The inventors of the present invention have made intensive studies to achieve the above object, and as a result, by including a zinc complex of a hydrazide compound having a specific structure in a rubber composition, the In the product, it was found that breakage due to reversion of sulfur bridges formed by vulcanization can be suppressed (improved reversion resistance).

Based on this knowledge, the present inventors have further studied and completed the present invention.

That is, the present invention provides the following zinc complex of a hydrazide compound and a reversion inhibitor for rubber containing a zinc complex of a hydrazide compound.

Section 1.
A zinc complex of a hydrazide compound represented by the following formula (1).

〔式（1）中、R¹、及びR²は、同一、又は異なって、各々、水素原子、又は炭素数1～6のアルキル基を示す。Aは、フェニル基、又はナフチル基を示し、少なくとも1つの極性基を有する。〕
項２．
前記式（1）で表されるヒドラジド化合物が、3-ヒドロキシ-N'-（4-メチルペンタン-2-イリデン）ナフタレン-2-カルボヒドラジド、又は2-ヒドロキシ-N'-（4-メチルペンタン-2-イリデン）安息香酸ヒドラジドである、前記項1に記載の亜鉛錯体。

[In Formula (1), R ¹ and R ² are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. A represents a phenyl group or a naphthyl group and has at least one polar group. ]
Section 2.
The hydrazide compound represented by the formula (1) is 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide or 2-hydroxy-N'-(4-methylpentane 2-ylidene)benzoic acid hydrazide, the zinc complex according to the above item 1.

Item 3.
A reversion inhibitor for rubber containing a zinc complex of a hydrazide compound represented by the following formula (1).

〔式（1）中、R¹、及びR²は、同一、又は異なって、各々、水素原子、又は炭素数1～6のアルキル基を示す。Aは、フェニル基、又はナフチル基を示し、少なくとも1つの極性基を有する。〕
項４．
前記式（1）で表されるヒドラジド化合物が、3-ヒドロキシ-N'-（4-メチルペンタン-2-イリデン）ナフタレン-2-カルボヒドラジド、又は2-ヒドロキシ-N'-（4-メチルペンタン-2-イリデン）安息香酸ヒドラジドである、前記項3に記載のゴム用加硫戻り抑制剤。

[In Formula (1), R ¹ and R ² are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. A represents a phenyl group or a naphthyl group and has at least one polar group. ]
Section 4.
The hydrazide compound represented by the formula (1) is 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide or 2-hydroxy-N'-(4-methylpentane 4. The reversion inhibitor for rubber according to the item 3, which is 2-ylidene)benzoic acid hydrazide.

The zinc complex of the hydrazide compound of the present invention and the reversion inhibitor for rubber containing the zinc complex of the hydrazide compound are formed by vulcanization in the rubber composition by including them in the rubber composition. Cutting due to reversion of sulfur bridges can be suppressed.

The present invention will be described in detail below.

As used herein, the terms "comprise" and "contain" include "comprise," "consist essentially of," and "consist of." It is a concept.

In this specification, when a numerical range is indicated by "A to B", the numerical range means A or more and B or less (from the numerical value of A to the numerical value of B).

[1] Hydrazide compound represented by formula (1) constituting zinc complex The hydrazide compound represented by formula (1) constituting the zinc complex of the hydrazide compound of the present invention is represented by the following structural formula. .

〔式（1）中、R¹、及びR²は、同一、又は異なって、各々、水素原子、又は炭素数1～6のアルキル基を示す。Aは、フェニル基、又はナフチル基を示し、少なくとも1つの極性基を有する。〕
式（1）中、R¹、及びR²は、同一、又は異なって、各々、水素原子、又は炭素数1～6のアルキル基を示す。

[In Formula (1), R ¹ and R ² are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. A represents a phenyl group or a naphthyl group and has at least one polar group. ]
In formula (1), R ¹ and R ² are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

The alkyl group having 1 to 6 carbon atoms is preferably a linear, branched or cyclic alkyl group. The number of carbon atoms in the alkyl group having 1 to 6 carbon atoms is preferably 1 to 4.

In formula (1), A represents a phenyl group or a naphthyl group and has at least one polar group.

In formula (1), the polar group possessed by A is not particularly limited. Polar groups are preferably amino groups, aminoalkyl groups, alkoxycarbonyl groups, acyl groups, acyloxy groups, amido groups, carboxyl groups, carboxyalkyl groups, formyl groups, nitrile groups, nitro groups, hydroxyalkyl groups, hydroxyl groups, alkoxy groups, aryloxy groups, heterocyclic groups, thiol groups, alkylthio groups, arylthio groups, and the like.

The polar group may have preferably 1 to 4, more preferably 1 to 3 at substitutable positions.

The amino group is preferably an amino group represented by _-NH2 .

Said amino group is preferably methylamino, ethylamino, n-propylamino, isopropylamino, n-butylamino, isobutylamino, s-butylamino, t-butylamino, 1-ethylpropylamino, n-pentylamino , neopentylamino, n-hexylamino, isohexylamino, 3-methylpentylamino, etc. Linear or branched monoalkylamino groups having 1 to 6 carbon atoms (substituted amino groups ).

The amino group is preferably a dialkylamino group (substituted amino group) having two linear or branched alkyl groups having 1 to 6 carbon atoms, such as dimethylamino, ethylmethylamino and diethylamino groups.

Among these polar groups, hydroxyl group, amino group and the like are preferable, and hydroxyl group is more preferable.

At least one of these polar groups is preferably substituted on the carbon atom adjacent to the carbon atom to which the carbohydrazide group is attached.

In the rubber composition of the present invention, the hydrazide compound represented by formula (1) constituting the zinc complex of the hydrazide compound is preferably
3-Hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide:

2-ヒドロキシ-N'-（4-メチルペンタン-2-イリデン）安息香酸ヒドラジド：

2-Hydroxy-N'-(4-methylpentan-2-ylidene)benzoic acid hydrazide:

である。

is.

In the rubber composition of the present invention, the zinc complex of the hydrazide compound represented by formula (1) is preferably 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide. zinc complex, or zinc complex of 2-hydroxy-N'-(4-methylpentan-2-ylidene)benzoic acid hydrazide.

The zinc complex of the hydrazide compound represented by the formula (1) of the present invention is formed from 1 mol of zinc atoms per 2 mol of the hydrazide compound represented by the formula (1).

[2] Rubber vulcanization reversion inhibitor The rubber vulcanization reversion inhibitor of the present invention is a zinc complex of a hydrazide compound represented by the following formula (1):

〔式（1）中、R¹、及びR²は、同一、又は異なって、各々、水素原子、又は炭素数1～6のアルキル基を示す。Aは、フェニル基、又はナフチル基を示し、少なくとも1つの極性基を有する。〕
を含む。

[In Formula (1), R ¹ and R ² are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. A represents a phenyl group or a naphthyl group and has at least one polar group. ]
including.

The details of the zinc complex of the hydrazide compound represented by formula (1) are as described in (1) hydrazide compound represented by formula (1) constituting the zinc complex .

In the rubber reversion inhibitor of the present invention, the zinc complex of the hydrazide compound represented by the formula (1) is preferably 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene- A zinc complex of 2-carbohydrazide or a zinc complex of 2-hydroxy-N'-(4-methylpentan-2-ylidene)benzoic acid hydrazide.

The zinc complex of the hydrazide compound of the present invention and the reversion inhibitor for rubber containing the zinc complex of the hydrazide compound are formed in the rubber composition by vulcanization by incorporating it into the rubber composition. It is possible to suppress breakage due to reversion of sulfur crosslinks, that is, to improve reversion resistance of the rubber composition.

[3] Components that can be applied to the rubber reversion inhibitor Components that can be applied to the rubber vulcanization reversion inhibitor of the present invention include diene rubber components, fillers, and the like. A reversion inhibitor for rubber containing a zinc complex of a hydrazide compound represented by formula (1) can be applied to a rubber composition containing a diene rubber component and a filler.

[3-1] Diene rubber component The diene rubber component is preferably natural rubber (NR), synthetic diene rubber, a mixture of natural rubber and synthetic diene rubber, or the like.

From the viewpoint of improving the durability of a rubber composition containing a diene rubber component, natural rubber is preferably used. In 100% by mass of the diene rubber component, natural rubber is preferably contained in an amount of 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and particularly preferably Contains 70% to 100% by mass.

The natural rubber is preferably natural rubber such as natural rubber latex, technical grade rubber (TSR), smoked sheet (RSS), gutta percha, Eucommia derived natural rubber, guayule derived natural rubber, Russian dandelion derived natural rubber. Natural rubber is preferably modified natural rubber such as epoxidized natural rubber, methacrylic acid-modified natural rubber, styrene-modified natural rubber and the like.

The synthetic diene rubber is preferably styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), nitrile rubber (NBR), chloroprene rubber (CR), ethylene-propylene-diene Original copolymer rubber (EPDM), styrene-isoprene-styrene triblock copolymer (SIS), styrene-butadiene-styrene triblock copolymer (SBS), etc., these modified synthetic diene rubbers, etc. .

The modified synthetic diene rubber is preferably a diene rubber obtained by modification techniques such as main chain modification, single terminal modification, and both terminal modification.

The modified functional group of the modified synthetic diene rubber is preferably a functional group containing a hetero atom such as an epoxy group, an amino group, an alkoxy group, or a hydroxyl group, and preferably contains one or more of these functional groups.

The ratio of cis/trans/vinyl in the diene moiety is not particularly limited, and any ratio is preferred.

The weight-average molecular weight and molecular weight distribution of the diene-based rubber are not particularly limited, and the weight-average molecular weight is preferably from 150,000 to 1,400,000.

The method for producing the synthetic diene rubber is not particularly limited, and is preferably a synthesis method such as emulsion polymerization, solution polymerization, radical polymerization, anionic polymerization, or cationic polymerization.

The synthetic diene rubber is preferably IR, SBR, BR, or a mixture of two or more selected from these, more preferably SBR, BR, or a mixture of two or more selected from these. The synthetic diene rubber is particularly preferably a diene rubber containing a structure obtained by polymerizing 1,3-butadiene.

The glass transition point of the synthetic diene rubber (preferably a diene rubber containing a structure obtained by polymerizing 1,3-butadiene) is preferably -110°C to -20°C from the viewpoint of achieving both wear resistance and braking characteristics. °C, more preferably -70°C to -20°C.

[3-2] Compounding amount of zinc complex of hydrazide compound In the rubber composition containing a diene rubber component, the compounding ratio of the zinc complex of the hydrazide compound represented by formula (1) to the diene rubber component is With respect to 100 parts by mass of the rubber component, it is preferably 0.05 to 30 parts by mass, more preferably 0.1 to 10 parts by mass, still more preferably 0.15 to 5 parts by mass, especially Preferably, it is 0.5 parts by mass to 2 parts by mass.

In a rubber composition containing a diene rubber component, when using a rubber reversion inhibitor containing a zinc complex of a hydrazide compound represented by formula (1), the formula contained in the rubber reversion inhibitor Based on the content of the zinc complex of the hydrazide compound represented by (1), the blending ratio of the zinc complex of the hydrazide compound represented by formula (1) to the diene rubber component may be adjusted at the aforementioned ratio. .

In the rubber composition of the present invention, the zinc complex of the hydrazide compound represented by the formula (1) is blended with the diene rubber component at the above ratio, so that the rubber composition is formed by vulcanization. In other words, excellent reversion resistance is exhibited.

Since the rubber composition of the present invention exhibits excellent reversion resistance, the use of the rubber composition of the present invention in a tire makes it possible to produce a tire exhibiting excellent durability.

[3-3] Filler The filler (reinforcing material) is preferably a conventionally known filler used in the rubber industry.

The filler is preferably an inorganic filler such as silica, carbon black, or the like.

The inorganic filler is preferably alumina (Al ₂ O ₃ ) such as silica, γ-alumina, α-alumina.

The inorganic _filler is preferably alumina monohydrate ( _Al2O3.H2O ) such as boehmite or _diaspore .

The inorganic filler is preferably aluminum hydroxide [Al(OH) ₃ ] such as gibbsite or bayerite.

The inorganic filler is preferably aluminum carbonate [ _Al2 ( _CO3 ) ₃ ], magnesium hydroxide [Mg(OH) ₂ ], magnesium oxide (MgO), magnesium carbonate ( _MgCO3 ), talc ( _3MgO.4SiO2・H ₂ O), attapulgite (5MgO 8SiO ₂ 9H ₂ O), titanium white (TiO ₂ ), titanium black (TiO _2n-1 ), calcium oxide (CaO), calcium hydroxide [Ca(OH) ₂ ] , aluminum magnesium _{oxide ( MgO.Al2O3 )} , _clay ( _{Al2O3.2SiO2 )} , kaolin ( _{Al2O3.2SiO2.2H2O )} , _{pyrophyllite ( Al2O3.4SiO2}・_H2O ), _bentonite ( _{Al2O3.4SiO2.2H2O} ) _, aluminum silicate _{( Al2SiO5} , _{Al4.3SiO4.5H2O} , _{etc. ) ,} magnesium _silicate ( _Mg2SiO4 , MgSiO3 _, etc.), calcium silicate (Ca2.SiO4 _{, etc.} ), aluminum calcium _silicate ( _{Al2O3.CaO.2SiO2} , _{etc. )} , magnesium calcium silicate ( _CaMgSiO4 ), calcium carbonate ( _CaCO3 ) , zirconium oxide (ZrO ₂ ), zirconium hydroxide [ZrO(OH) ₂ .nH ₂ O], zirconium carbonate [Zr(CO ₃ ) ₂ ], hydrogen, alkali metals, or alkalis that compensate charge like various zeolites and crystalline aluminosilicates containing earth metals.

As the inorganic filler, in order to improve the affinity with the rubber component, it is preferable to use an inorganic filler whose surface is organically treated.

The silica inorganic filler is preferably silica from the viewpoint of damping properties.

The BET specific surface area of silica is not particularly limited, and preferably ranges from 40 m ² /g to 350 m ² /g. Silica having a BET specific surface area within this range has the advantage of being able to achieve both rubber reinforcing properties and dispersibility in the rubber component.

The BET specific surface area is measured according to ISO 5794-1.

The range of BET specific surface area of silica is preferably 40 m ² /g to 350 m ² /g, more preferably 100 m ² /g to 270 m ² /g, particularly preferably 110 m ² /g to 270 m 2 /g. ² /g.

Commercially available products of silica include, for example, Quechen Silicon Chemical Co., Ltd. trade names “HD165MP” (BET specific surface area = 165 m ² /g), “HD115MP” (BET specific surface area = 115 m ² /g), “HD200MP "(BET specific surface area = 200 m ² /g), "HD250MP" (BET specific surface area = 250 m ² /g), trade name "Nip Seal AQ" manufactured by Tosoh Silica Co., Ltd. (BET specific surface area = 205 m ² /g), "Nip Seal KQ" (BET specific surface area = 240 m ² /g), Degussa's product name "Ultrasil VN3" (BET specific surface area = 175 m ² /g), and the like.

Carbon black Carbon black is not particularly limited, and examples thereof include commercially available carbon black and Carbon-Silica Dual phase filler.

The carbon black is preferably high, medium or low structure SAF, ISAF, IISAF, N110, N134, N220, N234, N330, N339, N375, N550, HAF, FEF, GPF, SRF grade carbon black etc. .

The carbon black is preferably SAF, ISAF, IISAF, N134, N234, N330, N339, N375, HAF, FEF grade carbon black.

The DBP absorption range of carbon black is not particularly limited, preferably 60 cm ³ /100 g to 200 cm ³ /100 g, more preferably 70 cm ³ /100 g to 180 cm ³ /100 g, particularly preferably 80 cm ³ /100 g to 160 cm ³ /100 g.

The nitrogen adsorption specific surface area of carbon black (measured according to NSA, JIS K 6217-2: 2001) is preferably in the range of 30 m ² /g to 200 m ² /g, more preferably 40 m ² / g to 180 m ² /g, particularly preferably 50 m ² /g to 160 m ² /g.

One type of filler may be used alone, or two or more types may be used in combination.

Amount of filler compounded The amount of filler compounded is preferably 10 parts by mass to 160 parts by mass, more preferably 20 parts by mass to 100 parts by mass, with respect to 100 parts by mass of the diene rubber component, More preferably, it is 30 parts by mass to 70 parts by mass.

[3-4] Other Components Components that can be applied to the rubber reversion inhibitor of the present invention include, in addition to the diene rubber component and the filler, those commonly used in the rubber industry. Add compounding agents.

Ingredients preferably include antioxidants, antiozonants, softeners, processing aids, waxes, resins, blowing agents, oils, stearic acid, zinc white (ZnO), vulcanization accelerators, vulcanization retarders, A vulcanizing agent (sulfur) or the like is appropriately selected and blended.

When silica is used as a filler, a silane coupling agent is preferably blended for the purpose of increasing the reinforcing properties of the rubber composition with silica, and for the purpose of increasing the low heat build-up and abrasion resistance of the rubber composition. The silane coupling agent is preferably a sulfide-based, polysulfide-based, thioester-based, thiol-based, olefin-based, epoxy-based, amino-based, or alkyl-based silane coupling agent.

[4] Tires The zinc complex of a hydrazide compound of the present invention and the reversion inhibitor for rubber containing the zinc complex of a hydrazide compound are added to the rubber composition so that the rubber composition does not undergo vulcanization. Suppresses breakage due to reversion of the formed sulfur bridge, that is, exhibits excellent reversion resistance.

The zinc complex of the hydrazide compound of the present invention and the reversion inhibitor for rubber containing the zinc complex of the hydrazide compound are contained in a rubber composition, and the rubber composition is used to manufacture a tire, resulting in excellent It is possible to manufacture a tire that exhibits excellent durability.

The use of the tire of the present invention is preferably tires for trucks, buses, heavy loads, winter tires, and the like.

In the tire of the present invention, the rubber composition is preferably used for at least one member selected from the tread portion, sidewall portion, bead area portion, belt portion, carcass portion and shoulder portion.

In the tire (pneumatic tire) of the present invention, more preferably, members such as the tread portion, bead area portion, belt portion and carcass portion are formed from the rubber composition of the present invention.

In the tire of the present invention, the rubber composition is particularly preferably used in the tread portion. The tread portion, which has a tread pattern and is in direct contact with the road surface, is the outer skin portion of the tire that protects the carcass and prevents abrasion and damage. The tread portion refers to a cap tread that constitutes the ground contact portion of the tire and/or a base tread that is provided inside the cap tread.

In the tire of the present invention, the rubber composition is preferably used for the bead area portion, belt portion, carcass portion, shoulder portion and the like.

The bead area portion is a portion that serves to fix both ends of the carcass cord and to fix the tire to the rim at the same time. A bead is a bundled structure of high carbon steel. The belt portion is a reinforcing band stretched circumferentially between the radially structured tread and the carcass. The carcass is strongly tightened like a hoop on a bucket, increasing the rigidity of the tread. The carcass portion is a portion of the cord layer that forms the frame of the tire, and plays a role in withstanding the load, impact, and filling air pressure that the tire receives. The shoulder portion is the shoulder portion of the tire and serves to protect the carcass.

In the tire of the present invention, the rubber composition is preferably used in the sidewall portion. The sidewall portion is a portion of the pneumatic radial tire from the lower side of the shoulder portion to the bead portion. The sidewall portion protects the carcass and is the portion that bends the most during running.

The tire of the invention is preferably manufactured according to methods known in the field of tires. As the gas to be filled in the tire, an inert gas such as air, nitrogen, argon, helium, etc., which is normal or whose oxygen partial pressure is adjusted, is preferably used.

[5] Method for producing the rubber composition The method for producing the rubber composition is not particularly limited. Preferably, the compound, rubber component, filler, and, if necessary, other components are mixed. can be done.

The mixing method is not particularly limited, and preferably the compound, rubber component, filler, and other components as necessary are kneaded using a kneader or the like.

Although embodiments of the invention have been described, the invention is in no way limited to such examples. Various forms can be implemented without departing from the gist of the present invention.

Embodiments of the present invention will be described more specifically based on Production Examples and Examples.

The present invention is not limited to these.

[1] Manufacture of hydrazide compounds
Compound 1: 3-Hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide 3- Hydroxynaphthalene-2-carbohydrazide was added to a 500 mL four-necked flask equipped with a Dean-Stark apparatus. (manufactured by Tokyo Kasei Kogyo Co., Ltd.) and 138 mL of 4-methyl-2-pentanone were added to form a suspension, which was heated to around 116°C for 3 hours while removing the generated water using a Dean-Stark apparatus. Heated to reflux.

The reaction solution was cooled at a cooling rate of 1.7°C/min while being stirred at 250 rpm, crystals were precipitated at 80°C, and immediately cooled to 5°C at a rate of 1.7°C/min. The precipitated crystals were collected by filtration and dried under reduced pressure to give 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide as pale brown crystals.

Melting point 157.4℃
¹ H NMR (300 MHz, CDCl ₃ ) δ: 0.8-1.1 (6H), 1.8-2.4 (6H), 7.2-7.8 (5H), 8.4-8.5 (1H), 10.2-11.0 (1H) Not detected.

¹ H NMR spectrum was detected as an isomeric mixture.

Compound 2: 2-Hydroxy-N ' -(4-methylpentan-2-ylidene)benzoic acid hydrazide A 300 mL eggplant-shaped flask equipped with a condenser was charged with 5.00 g of salicylic acid hydrazide (manufactured by Tokyo Chemical Industry Co., Ltd.) and 100 mL of methanol. was added to form a suspension, 3.95 g of 4-methyl-2-pentanone was added, and the mixture was heated under reflux overnight.

After the reaction solution was concentrated under reduced pressure, the precipitated solid was filtered and washed with a mixed solvent of hexane and ethyl acetate. The obtained solid was dried under reduced pressure to obtain 7.50 g (97% yield) of 2-hydroxy-N'-(4-methylpentan-2-ylidene)benzoic acid hydrazide as a white solid.

Melting point 158℃
¹ H NMR (500 MHz, CDCl ₃ ) δ: 0.9-1.1 (6H), 1.8-2.4 (6H), 6.8-6.9 (1H), 7.0 (1H), 7.4-7.5 (2H), 8.7-9.2 (1H) , 10.3 to 13.0 (1H)
¹ H NMR spectrum was detected as an isomeric mixture.

[2] Production of zinc complex of hydrazide compound
Zinc complex of compound 1: zinc complex of 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide (compound 3)
Put 10 g of 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide and 200 mL of methanol into a 300 mL eggplant-shaped flask equipped with a condenser to make a solution, and add zinc acetate dihydrate. A 90 mL methanol solution containing 7.72 g of the soda was added dropwise.

The reaction solution was heated with stirring at 50° C. for 5 hours and further stirred at room temperature overnight. The precipitated solid was filtered and washed with 50 mL of methanol. The obtained solid was dried under reduced pressure to obtain 10.38 g (93% yield) of a zinc complex of 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide as a yellow solid.

Melting point 250°C or higher From changes in melting point and color, it was confirmed that a zinc complex of 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide was produced.

Zinc complex of compound 2: zinc complex of 2-hydroxy-N'-(4-methylpentan-2-ylidene)benzoic hydrazide (compound 4)
3.00 g of 2-hydroxy-N'-(4-methylpentan-2-ylidene)benzoic acid hydrazide and 40 mL of methanol are added to a 200 mL eggplant-shaped flask equipped with a condenser to form a solution, zinc acetate dihydrate. 2.81 g of methanol in a volume of 30 mL was added dropwise, and the mixture was heated and stirred at 50° C. overnight.

The reaction solution was allowed to cool to room temperature, and the precipitated solid was filtered and washed with 20 mL of methanol. The obtained solid was dried under reduced pressure to obtain 1.72 g (51% yield) of a zinc complex of 2-hydroxy-N'-(4-methylpentan-2-ylidene)benzoic acid hydrazide as a white solid.

Melting point 250°C or higher From the change in melting point, it was confirmed that a zinc complex of 2-hydroxy-N'-(4-methylpentan-2-ylidene)benzoic acid hydrazide was produced.

[3] Measurement of hydrazide content and zinc content of zinc complex of hydrazide compound
[3-1] Hydrazide content (mass) in zinc complex of hydrazide compound
Measured by HPLC analysis.

Zinc complex of compound 1: zinc complex of 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide (compound 3)
Preparation of test sample solution: 10 mL of tetrahydrofuran was added to 10 mg of the zinc complex to dissolve it, and diluted with methanol to a constant volume.

Conditions for HPLC analysis:
Column: GL Sciences Inc., Inertsil (R) ODS-3 4.6 mm × 250 mm, 5 μm
Injection volume: 5 μL
Detection wavelength: 254nm
Column temperature: 40℃
Mobile phase: methanol/phosphate buffer = 60/40 (Vol)
A phosphate buffer was prepared by dissolving 6 mmol disodium hydrogen phosphate and 6 mmol potassium dihydrogen phosphate in 1 L of distilled water.

Flow rate: 1mL/min
Retention time: Detected as 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide at approximately 10 min.

Zinc complex of compound 2: zinc complex of 2-hydroxy-N'-(4-methylpentan-2-ylidene)benzoic hydrazide (compound 4)
Preparation of test sample solution: 10 mL of tetrahydrofuran was added to 10 mg of the zinc complex to dissolve it, and diluted with methanol to a constant volume.

Conditions for HPLC analysis:
Column: GL Sciences Inc., Inertsil (R) ODS-3 4.6 mm × 250 mm, 5 μm
Injection volume: 5 μL
Detection wavelength: 254nm
Column temperature: 40℃
Mobile phase: methanol/phosphate buffer = 55/45 (Vol)
A phosphate buffer was prepared by dissolving 6 mmol disodium hydrogen phosphate and 6 mmol potassium dihydrogen phosphate in 1 L of distilled water.

Flow rate: 1mL/min
Retention time: Detected as 2-hydroxy-N'-(4-methylpentan-2-ylidene)benzoic acid hydrazide at approximately 15 min.

[3-2] Zinc content (mass) in zinc complex of hydrazide compound
It was measured by chelate titration.

Zinc complex of compound 1: zinc complex of 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide (compound 3)
Chelate titration conditions:
About 100 mg of the zinc complex was precisely weighed, dissolved in 2 mL of N,N-dimethylformamide, and diluted with 10 mL of methanol. Furthermore, 40 mL of water, 10 mL of acetic acid/sodium acetate buffer of pH 5, and 0.5 mL of XO reagent were added to obtain a pink suspension. A 0.1 mol/L disodium EDTA solution was added dropwise to perform chelate titration until the pink color of the suspension changed to yellow.

Zinc complex of compound 2: zinc complex of 2-hydroxy-N'-(4-methylpentan-2-ylidene)benzoic hydrazide (compound 4)
Chelate titration conditions:
Chelate titration was performed in the same manner as the zinc complex of 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide.

Table 1 shows the hydrazide content, zinc content and content ratio (mass ratio) in the zinc complexes of various hydrazide compounds.

Compound 1: 3-Hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide Compound 2: 2-Hydroxy-N'-(4-methylpentan-2-ylidene)benzoic acid hydrazide Compound 3: Zinc complex of compound 1 Compound 4: Zinc complex of compound 2

[4] Examples 1 and 2 and Comparative Examples 1 and 2: Production of rubber composition Each component shown in Table 2 was mixed in its ratio (parts by mass) and kneaded in a plastomill to prepare a rubber composition. . Each prepared rubber composition was evaluated for reversion resistance by the following method.

The vulcanization curve of the unvulcanized rubber obtained by kneading with a reversion-resistant plastomill was measured at 150° C. for 60 minutes with a vulcanization tester (manufactured by M&K Co., Ltd.). The maximum torque due to vulcanization was defined as "MH", the torque after 60 minutes was defined as "M60", and the reversion resistance was quantified by the following formula.

Reversion resistance = (MH-M60)/MH
The resistance to reversion was represented by an index representing the resistance to reversion quantified. The reversion resistance index of the example (zinc complex of hydrazide compound) was expressed with the index of reversion resistance of the comparative example (hydrazide compound) serving as a comparative object being 100.

Reversion resistance index of Example (zinc complex of hydrazide compound) = Reversion resistance of Example (zinc complex of hydrazide compound)/Reversion resistance of Comparative Example (hydrazide compound) x 100
Reversion resistance index of Example 1 (Compound 3) = Reversion resistance of Example 1 (Compound 3)/Reversion resistance of Comparative Example 1 (Compound 1) × 100
Reversion resistance index of Example 2 (Compound 4) = Reversion resistance of Example 2 (Compound 4)/Reversion resistance of Comparative Example 2 (Compound 2) × 100
As for reversion resistance, the smaller the value of the index, the lower the reduction rate from the maximum value of torque, indicating that the sulfur bridges are not broken due to reversion. It means that it is good.

Table 2 shows the evaluation results.

*1：N234グレード
*2：N-（1,3-ジメチルブチル）-N'-フェニル-p-フェニレンジアミン（6PPD）
*3：N-シクロヘキシル-2-ベンゾチアリルスルフェンアミド（CBS）
*4：化合物1
*5：化合物2
*6：化合物3（化合物1の亜鉛錯体）
*7：化合物4（化合物2の亜鉛錯体）

*1: N234 grade
*2: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD)
*3: N-Cyclohexyl-2-benzothiarylsulfenamide (CBS)
*4: Compound 1
*5: Compound 2
*6: Compound 3 (zinc complex of compound 1)
*7: Compound 4 (zinc complex of compound 2)

The zinc complex of the hydrazide compound of the present invention and the reversion inhibitor for rubber containing the zinc complex of the hydrazide compound exhibit excellent reversion resistance by incorporating them into the rubber composition.

The zinc complex of the hydrazide compound of the present invention and the reversion inhibitor for rubber containing the zinc complex of the hydrazide compound are contained in a rubber composition, and the rubber composition is used to manufacture a tire, resulting in excellent It is possible to manufacture a tire that exhibits excellent durability.

Claims (4)

A zinc complex of a hydrazide compound represented by the following formula (1).

[In Formula (1), R ¹ and R ² are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. A represents a phenyl group or a naphthyl group and has at least one polar group. ] The hydrazide compound represented by the formula (1) is 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide or 2-hydroxy-N'-(4-methylpentane -2-ylidene)benzoic acid hydrazide according to claim 1. A reversion inhibitor for rubber containing a zinc complex of a hydrazide compound represented by the following formula (1).

[In Formula (1), R ¹ and R ² are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. A represents a phenyl group or a naphthyl group and has at least one polar group. ] The hydrazide compound represented by the formula (1) is 3-hydroxy-N'-(4-methylpentan-2-ylidene)naphthalene-2-carbohydrazide or 2-hydroxy-N'-(4-methylpentane 4. The rubber reversion inhibitor according to claim 3, which is 2-ylidene)benzoic acid hydrazide.